This report describes continuing studies in which the cellular and intracellular mechanisms of carbohydrate metabolism and transport are being examined. The investigation has shown that there are problems in obtaining an accurate in vivo calibration of microdialysis probes in brain tissue. Without an accurate calibration of the probes the estimates of the steady- state concentrations of glucose and other carbohydrates in the extracellular space will be too inaccurate to be useful. In the interim until this problem can be solved, experiments that take advantage of the use of the microdialysis probe but in a somewhat different area have been undertaken. These latter experiments examine the effects of nitric oxide on local cerebral blood flow (CBF); these studies are timely inasmuch as this compound has recently been shown by in vitro experiments to be similar to or identical with the Endothelium-Derived Relaxing Factor (EDRF) and may represent the missing link to explain the close coupling of local cerebral blood flow to local functional and metabolic activities.